Move local ports management from Call to SIPCall class

Call class is an ABC and not supposed to know and even more handles
how it's connected to the peer.
This is the purpose of concrete classes as SIPCall.

To respect this design local ports members and related API,
used for medias, are removed from Call and re-implemented
into SIPCall.

Notice the removal of mutex use, not required as read and write are
done in the same calling flow, and also the better RING_VIDEO define
checks around localVideoPort_.

Change-Id: I1feefe20a45f6b89b2eab448be78cd525e7a28c7